As RJ Safra writes on MintLife, investment games can teach you about your own investment style and possible red flags:

I dumped a few other stocks I had collected along the way. I realized that I was holding them waiting for them to go back up. And it occurred to me that this had become my favorite excuse: "That one is long-term," I always tell myself when it goes down. Then I hold the rotten stock even if my rationale for buying it proves flawed.

Knowing yourself means you become your own worst critic when it comes to your money. Be brutal. Once that stock is sunk money let it sink.

A practice run can help you learn not to go all out on buying stocks or warn you against buying the wrong kinds of investments just because they're available to you. Use an investment simulator to develop the patience and prudence you might not get from trading with your own hard-earned money.